Carbon fiber reinforced base material, preform and composite material comprising the same

ABSTRACT

A carbon fiber reinforced substrate comprising a fabric composed of carbon fiber bundles and a first resin adhering to the fabric. Each of the carbon fiber bundles comprises numerous continuous carbon filaments, has the tensile modulus of 210 GPa or more, and has the fracture strain energy of 40 MJ/m 3  or more. The amount of the first resin adhering to the fabric is in a range from 1 to 20 parts by weight per 100 parts by weight of said fabric. A preform comprising a laminate composed of plural layers of the carbon fiber reinforced substrate, wherein the layers are integrated by means of the first resin. A composite comprising the preform impregnated with a matrix resin.

TECHNICAL FIELD

[0001] The present invention relates to a carbon fiber reinforcedsubstrate, a preform comprising the substrate, and a compositecomprising the preform.

[0002] The present invention relates to a carbon fiber reinforcedsubstrate having excellent handling properties at forming a preform fromthe carbon fiber reinforced substrate. The handling properties mean atleast any one property selected from the stiffness, form stability,drapability and tackiness in lamination, of the carbon fiber reinforcedsubstrate.

[0003] The invention also relates to a preform having excellent resinpermeability at forming a composite from the carbon fiber reinforcedsubstrate having such excellent handling properties.

[0004] Furthermore, the invention relates to a composite havingexcellent mechanical properties, which is formed from the preform havingexcellent resin permeability. The mechanical properties mean at leastone property selected from the compression strength after impact and thecompression strength after hot-wet conditioning.

BACKGROUND ART

[0005] Composites reinforced with carbon fibers have been used inapplications of aircraft, space and sports, because of their excellentmechanical properties and lightweight.

[0006] As a typical method of producing such a composite, autoclavemolding is known. In the method, a prepreg comprising a sheet composedof carbon fiber bundles each of which is formed with continuous carbonfibers arranged in one direction and a matrix resin being impregnatedtherewith. The prepregs are piled up in a mold and heated andpressurized in an autoclave, to be made into a composite.

[0007] The prepreg used as a substrate to be molded into a composite hasan advantage in production of composite having high reliability.However, it also has a disadvantage that it is too stiff to be drapable.Furthermore, the production of a composite using the prepreg has suchproblems as high cost and low productivity.

[0008] For molding a composite at high productivity, injection moldingor infusion molding is known. The injection or infusion moldingincludes, for example, resin transfer molding (RTM). In the resintransfer molding (RTM), a substrate composed of carbon fiber bundles notpre-impregnated with a matrix resin (dry carbon fiber bundles) is placedin a complicatedly shaped mold, and a matrix resin liquid (lowviscosity) is injected or infused into the mold, for making the carbonfiber bundles impregnated with the matrix resin.

[0009] However, though the injection or infusion molding is excellent incomposite productivity, the substrate used (for example, a dry wovenfabric) has problems in view of handling properties such that textureslippage is liable to occur (un-stability of form), that the substrateis so less stiff as to allow easy bending, and that layers of thesubstrate do not adhere to each other when laminated (no tackyproperty). In addition, since the matrix resin must be low in viscosity,the composite has a problem of being low in mechanical properties,compared with the composite formed with a matrix resin having a highviscosity as used in the above-mentioned prepreg. These problems presenta problem that the composite obtained cannot sufficiently exhibit theproperties peculiar to carbon fibers and does not have the mechanicalproperties expected from the properties of the carbon fibers used.

[0010] To solve this problem, U.S. Pat. No. 5,071,711 A proposes atechnique, in which a thermoplastic-like resin is applied to a fabriccomposed of reinforcing fibers, for improving the handling properties ofthe dry woven fabric used as a substrate, and stabilizing the form ofthe preform used for injection or infusion molding.

[0011] Furthermore, Journal of Advanced Materials, Volume 32, No. 3,Jul. 2000, P27-34 or Composites Part A, Volume 32, 2001, P721-729reports that if a woven fabric is coated with a resin obtained by mixingan epoxy resin and elastomer particles or polyamide 6, for injection orinfusion molding, the mechanical properties (such as the interlaminarfracture toughness of Mode II) of the obtained CFRP are improved.

[0012] However, the proposal cannot improve, or can improve onlyinsufficiently, mechanical properties, though it can improve thehandling properties of the substrate. That is, for example, the veryhigh levels of mechanical properties required for primary or principalstructure elements of aircraft cannot be achieved even if a woven fabricor the like is merely coated with a resin, and in the case where thecarbon fibers used themselves do not have the necessary properties, thecomposite obtained using them cannot exhibit necessary mechanicalproperties (especially the compression strength after impact) either.

[0013] Moreover, in the injection or infusion molding methods describedin the above-mentioned proposals, since a sheet composed of carbon fiberbundles merely arranged in one direction cannot be handled with thefiber orientation kept as it is in a dry state, a bi-directional wovenfabric is used.

[0014] However, for example, primary or principal structure elements ofaircraft require very high mechanical properties, especially thecompression strength after impact and the compression strength afterhot-wet conditioning. In a bi-directional woven fabric, carbon fiberbundles form a bi-directional weave structure. Therefore, the amount ofreinforcing fibers in each direction is substantially one half.Furthermore, since the warp and the weft are almost equal in fineness ortiter, large crimps of carbon fiber bundles are formed at theinterlacing points of warp and weft. Because of these problems, themechanical properties of a prepreg composed of carbon fibers arranged intwo directions could be only halves of those of a prepreg composed ofcarbon fibers arranged in one direction.

[0015] That is, even though the required properties of the carbon fibersto be used and the form of the fabric composed of the carbon fibers areespecially important factors for exhibiting high mechanical properties,the above-mentioned proposals do not disclose any explanation about suchfactors at all.

[0016] The object of the invention is to solve the problems of the priorart. Particularly, the object of the invention is to provide a carbonfiber reinforced substrate having excellent handling properties in suchas stiffness, form stability, drapability and tackiness, to provide apreform formed with the substrate and having good matrix resinpermeability, and to provide a composite formed with the preform havingexcellent mechanical properties in such as the compression strengthafter impact or the compression strength after hot-wet conditioning, andhaving also good productivity.

DISCLOSURE OF THE INVENTION

[0017] The carbon fiber reinforced substrate of the invention comprisesa fabric composed of carbon fiber bundles and a first resin adhering tothe fabric, and is characterized in that the carbon fiber bundles eachof which comprises numerous continuous carbon filaments, that thetensile modulus of the carbon fiber bundles is 210 GPa or more, that thefracture strain energy of the carbon fiber bundles is 40 MJ/m³ or more,and that the amount of the first resin adhering to the fabric is in arange from 1 to 20 parts by weight per 100 parts by weight of thefabric.

[0018] It is preferable that the amount of the first resin is in a rangefrom 1 to 10 parts by weight per 100 parts by weight of the fabric.

[0019] It is preferable that the first resin adhering to the fabricadheres relatively more densely on a surface of the fabric than in theinside of the carbon fiber bundles.

[0020] It is preferable that the tensile modulus of the carbon fiberbundles is more than 280 and less than 500 GPa, and that the fracturestrain energy of the carbon fiber bundles is 53 MJ/m³ or more.

[0021] It is preferable that the fabric is a uni-directional wovenfabric, bi-directional woven fabric or uni-directional sheet, that thecarbon fiber unit weight of the carbon fiber reinforced substrate is ina range from 50 to 500 g/m², and that the thickness of the carbon fiberreinforced substrate is in a range from 0.1 to 0.8 mm.

[0022] It is preferable that the fabric is a uni-directional wovenfabric or uni-directional sheet, and that the air permeability of thecarbon fiber substrate is in a range from 10 to 200 cm³/cm²·sec.

[0023] It is preferable that the first resin is studded on a surface ofthe fabric, and that the diameters of the studded pieces are 1 mm orless.

[0024] It is preferable that the first resin discontinuously adheres ona surface of the fabric.

[0025] It is preferable that the first resin adheres on a surface of thefabric, and that the average thickness of the first resin adhering onthe surface is in a range from 5 to 250 μm.

[0026] It is preferable that the melting point or flow initiationtemperature of the first resin is in a range from 50 to 150° C.

[0027] It is preferable that the main component of the first resin is athermosetting resin.

[0028] It is preferable that the main component of the first resin is athermoplastic resin.

[0029] It is preferable that the amount of the thermoplastic resin is ina range from 70 to 100 wt % based on the weight of the first resin.

[0030] It is preferable that the main component of the first resin is atleast one selected from the group consisting of epoxy resins, polyamideresins, polyetherimide resins, polyphenylene ether resins, polyethersulfone resins and phenoxy resins.

[0031] It is preferable that the amount of a second resin higher inmelting point or flow initiation temperature than the first resin andadhering to the fabric is in a range from 1 to 10 parts by weight per100 parts by weight of the fabric.

[0032] It is preferable that the amount of a second resin neither moltennor caused to flow at the melting point or flow initiation temperatureof the first resin and adhering to the fabric is in a range from 1 to 10parts by weight per 100 parts by weight of the fabric.

[0033] It is preferable that the second resin adheres on a surface ofthe fabric by means of the first resin.

[0034] It is preferable that the second resin is particles having anaverage particle diameter of 1 to 500 μm.

[0035] It is preferable that the main component of the second resin is athermoplastic resin.

[0036] It is preferable that the main component of the second resin isat least one thermoplastic resin having a glass transition temperatureof 30 to 280° C. selected from the group consisting of polyamide resins,polyamideimide resins, polyetherimide resins and polyether sulfoneresins.

[0037] The preform of the invention is a laminate comprising at leasttwo or more layers of the carbon fiber reinforced substrate, wherein thelayers of the carbon fiber reinforced substrate are integrally bonded toeach other by means of the first resin or the second resin.

[0038] The composite of the invention comprises at least the preform anda third resin, wherein the preform is impregnated with the third resindifferent from the first resin.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039]FIG. 1 is a typical plan view showing a mode of the carbon fiberreinforced substrate of the invention.

[0040]FIG. 2 is a typical plan view showing another mode of the carbonfiber reinforced substrate of the invention.

[0041]FIG. 3 is a typical vertical sectional view showing yet anothermode of the carbon fiber reinforced substrate of the invention.

[0042]FIG. 4 is a typical vertical sectional view showing a stillfurther mode of the carbon fiber reinforced substrate of the invention.

[0043]FIG. 5 is a perspective view showing another mode (uni-directionalwoven fabric) of the fabric used in the carbon fiber reinforcedsubstrate of the invention.

[0044]FIG. 6 is a perspective view showing yet another mode(uni-directional woven fabric) of the fabric used in the carbon fiberreinforced substrate of the invention.

[0045]FIG. 7 is a typical vertical sectional view showing a stillfurther mode of the carbon fiber reinforced substrate of the invention.

[0046]FIG. 8 is a typical vertical sectional view showing a stillfurther mode of the carbon fiber reinforced substrate of the invention.

[0047]FIG. 9 is a typical vertical sectional view showing a mode of thepreform of the invention.

[0048]FIG. 10 is a typical vertical sectional view showing a mode of thecomposite of the invention.

[0049]FIG. 11 is a schematic perspective view showing primary structureelements of an aircraft.

[0050]FIG. 12 is a schematic perspective view showing an example of astructural element in which the composite of the invention is applied.

[0051]FIG. 13 is a schematic perspective view showing another example ofa structural element in which the composite of the invention is applied.

MEANINGS OF SYMBOLS IN THE DRAWINGS

[0052]11, 21, 31, 41, 71, 81: a carbon fiber structure

[0053]12, 22, 32, 42, 52, 62, 72, 82: a warp yarn formed by carbonfibers

[0054]13, 33, 73: a weft yarn formed by carbon fibers

[0055]14, 24, 34, 44, 74, 84, 93, 103: a first resin

[0056]15, 25, 35, 45, 76, 86: a fabric

[0057]23, 43, 53, 63, 83: an auxiliary weft yarn formed by auxiliaryfibers

[0058]51, 61: a unidirectional woven fabric

[0059]64: an auxiliary warp yarn formed by auxiliary fibers

[0060]75, 85, 94, 104: a second resin

[0061]90: a carbon fiber substrate

[0062]91: a preform

[0063]92: a fabric composed of continuous carbon fibers

[0064]101: a composite

[0065]102: a third resin

[0066]111: an aircraft

[0067]112: a main wing

[0068]113: a keel beam

[0069]114: a fuselage

[0070]115: a vertical fin

[0071]116: a horizontal stabilizer

[0072]121, 131: a structure element

[0073]122, 132: a skin

[0074]123, 133: a spar

[0075]124, 134: a stiffener

THE MOST PREFERRED MODES FOR CARRYING OUT THE INVENTION

[0076] The carbon fiber reinforced substrate of the invention comprisesa fabric composed of carbon fiber bundles and a first resin adhering tothe fabric. The carbon fiber bundles respectively comprises numerouscontinuous carbon filaments. The carbon fiber bundles have a tensilemodulus of 210 GPa or more and a fracture strain energy of 40 MJ/m³ ormore. The amount of the first resin adhering to the fabric is in a rangefrom 1 to 20 parts by weight per 100 parts weight of the fabric.

[0077] The continuous carbon filaments mean that carbon filaments aresubstantially continuous in the fabric. The expression of beingsubstantially continuous is used in consideration that there is a casewhere a very small number of carbon filaments is broken during formingof a carbon fiber bundle or forming of a fabric.

[0078] The carbon fiber bundle in the carbon fiber substrate of theinvention has a tensile modulus of 210 GPa or more and a fracture strainenergy of 40 MJ/m³ or more.

[0079] It is preferable that the tensile modulus is more than 250 andless than 600 GPa, more preferably more than 280 and less than 500 GPa,and still more preferably more than 290 and less than 400 GPa.

[0080] If the tensile modulus is less than 210 GPa, the mechanicalproperties of the composite formed using the carbon fiber substrate arenot sufficient.

[0081] The tensile modulus is measured according to the measuring methodspecified in JIS-R-7601. The unit is GPa.

[0082] It is preferable that the fracture strain energy is 45 MJ/m³ ormore, more preferably 53 MJ/m³ or more, and still more preferably 56MJ/m³ or more. A higher fracture strain energy is desireable, however,based on usually available carbon fiber bundles at present, generallythe fracture strain energy is 80 MJ/m³ or less.

[0083] If the fracture strain energy is less than 40 MJ/m³, themechanical properties of the composite formed by the carbon fibersubstrate are not sufficient. That is, when the composite is impacted,there is a case where fracture occurs to the carbon fiber bundles. Themechanical properties can be judged in reference to the compressionstrength at room temperature after impact (hereinafter abbreviated asCAI).

[0084] Especially if the fracture strain energy is less than 40 MJ/m³,the composite having a quasi-isotropic stack architecture formed bylaminating plural uni-directional fabrics respectively having carbonfiber bundles arranged in one direction becomes very low in CAI.

[0085] The CAI of a composite is a mechanical property highly respectedwhen the composite is used as a structure element (especially as aprimary or principal structure element) of a transport machine(especially an aircraft). For using a composite as such a structureelement, recently it is highly demanded that the composite has anexcellent CAI.

[0086] The fracture strain energy (W) is calculated from equationW=σ²/2×E based on the tensile strength (σ) and tensile modulus (E)measured according to the measuring methods specified in JIS-R-7601. Theunit is MJ/m³ (10⁶×J/m³).

[0087] The amount of the first resin adhering to the fabric in thecarbon fiber substrate of the invention is in a range from 1 to 20 partsby weight per 100 parts by weight of the fabric. It is preferable thatthe amount is in a range from 1 to 10 parts by weight.

[0088] The first resin may exist inside the fabric, that is, between therespectively adjacent carbon fiber bundles or between the respectivelyadjacent carbon filaments in each carbon fiber bundle, or may bemaldistributed and adhere relatively more densely on a surface of thefabric rather than in the inside of the fabric.

[0089] Maldistribution means a state that the first resin of 70 vol % ormore, desirably 80 vol % or more, more desirably 90 vol % or more existson a surface of the fabric.

[0090] Adhesion of the first resin to the fabric in amount of from 1 to20 parts by weight per 100 parts by weight of the fabric brings tacky(adhesive) property between substrates at forming a perform bylaminating the carbon fiber reinforced substrates each other.Furthermore, a moderate stiffness is imparted to the fabric, and a formstability of the fabric is brought by preventing texture slippage of thecarbon fiber bundles in the fabric. As a result, a carbon fiberreinforced substrate having excellent handling properties can beobtained.

[0091] The first resin in the adhesive amount functions as a crackstopper in the composite obtained by laminating layers of the carbonfiber reinforced substrate and also functions to relax the thermalresidual stress when the composite is molded. Especially when thecomposite is impacted, the first resin functions to prevent theinterlaminar damage of the carbon fiber reinforced substrate, and givesexcellent mechanical properties (especially CAI, tensile strength andcompression strength), i.e., a toughening effect to the composite.

[0092] The carbon fiber reinforced substrate of the invention has beencompleted based on a finding that the toughening effect by the firstresin can be obtained when the first resin is used in combination withcarbon fiber bundles having a fracture strain energy of 40 MJ/m³ ormore.

[0093] In the case where carbon fiber bundles having a fracture strainenergy of 40 MJ/m³ or more are not used, the toughening effect by thefirst resin declines to such a non-detectably low level. On thecontrary, in the case where the deposited amount of the first resinadhering to the fabric is not in the above-mentioned range even if thecarbon fiber bundles are used, the toughening effect by the first resincannot be essentially exhibited.

[0094] In addition to the toughening effect, if the first resin adheresrelatively more densely on a surface of the fabric, the first resinadhering on the surface of the fabric functions as a spacer in the casewhere layers of the carbon fiber reinforced substrate are laminated oneach other, to form a space between the adjacent layers of the carbonfiber reinforced substrate. This is called the spacer effect by thefirst resin.

[0095] The spacer effect plays the role of forming flow paths for athird resin which is a matrix resin hereinafter explained, at molding ofa composite by injecting or infusing the third resin into the laminatedcarbon fiber substrates. The spacer effect facilitates the permeation ofthe third resin into the substrate, raises permeating speed, andenhances the composite productivity.

[0096] The spacer effect plays also the role to work on the tougheningeffect of the first resin intensively in the interlaminar portionbetween the substrate layers of the composite. As a result, a furtherhigher toughening effect can be achieved. This is called theinterlaminar toughening effect by the first resin. This effect was notexpected in the beginning.

[0097] The toughening effect, the spacer effect and the interlaminartoughening effect by the first resin are promoted still more bymaldistributing the first resin on a surface of the fabric.

[0098] The first resin may adhere relatively more densely on one surfaceof a single-layer fabric or on both surfaces of the fabric. The formeris preferable for producing a carbon fiber reinforced substrate havingthe first resin adhering relatively more densely to the fabric in alower cost. If it is not desired to discriminate the front and reversesurfaces of the carbon fiber substrate, the latter is desirable. In amultilayer fabric, the first resin may adhere to one surface each orboth surfaces each of the outermost layers, but it is preferable thatthe first resin adheres to the surfaces of the respective layers, sincehigher effects can be achieved.

[0099] In JP 6-94515 B or JP 5-337936 A, a technique on disposing a finepowder or a woven fabric on a surface of a prepreg used for autoclavemolding is disclosed. However, for the present invention intended forproviding a composite at a high productivity, autoclave molding is notsuitable. The handling properties such as stiffness and drapabilitycannot be achieved in the conventional prepreg. Since the conventionalprepreg is impregnated with a tacky matrix resin (corresponding to thethird resin described later), it is easy to dispose a powder and thelike on it for adhesion. However, quite a novel technical concept isnecessary for disposing a powder or the like on a dry and non-tackyfabric.

[0100] The present invention is described below more particularly inreference to drawings.

[0101]FIG. 1 is a typical plan view showing a mode of the carbon fiberreinforced substrate of the invention. In FIG. 1, a carbon fiberreinforced substrate 11 comprises a fabric 15 and a first resin 14adhering to the fabric 15. The fabric 15 comprises warp yarns 12 formedby carbon fiber bundles and weft yarns 13 formed by carbon fiberbundles, and the warp yarns 12 and the weft yarns 13 form the fabric 15in a plain weave. The fabric 15 is a kind of bi-directional wovenfabric. Each of the carbon fiber bundles used as the warp yarns 12 andthe weft yarns 13 respectively comprises numerous continuous carbonfilaments. The first resin 14 is studded on a surface of the fabric 15.

[0102]FIG. 2 is a typical plan view showing another mode of the carbonfiber reinforced substrate of the invention different from the mode ofFIG. 1. In FIG. 2, a carbon fiber reinforced substrate 21 comprises afabric 25 and a first resin 24 adhering to the fabric 25. The fabric 25comprises warp yarns 22 formed by carbon fiber bundles and auxiliaryweft yarns 23 formed by auxiliary yarns thinner than the warp yarns 22,and the warp yarns 22 and the auxiliary weft yarns 23 form the fabric 25in a plain weave. Since the fabric 25 is mainly composed of warp yarns22 formed by carbon fiber bundles, it is a kind of uni-directional wovenfabric. Each of the carbon fiber bundles used as the warp yarns 22comprises numerous continuous carbon filaments. The first resin 24adheres to a surface of the fabric 25 discontinuously.

[0103]FIG. 3 is a typical vertical sectional view showing yet anothermode of the carbon fiber reinforced substrate of the invention. In FIG.3, a carbon fiber reinforced substrate 31 comprises a fabric 35 and afirst resin 34 adhering to the fabric 35. The fabric 35 comprises warpyarns 32 formed by carbon fiber bundles and weft yarns 33 formed bycarbon fiber bundles, and the warp yarns 32 and the weft yarns 33-formthe fabric 35 in a plain weave. This fabric 35 is a kind ofbi-directional woven fabric. Each of the carbon fiber bundles used asthe warp yarns 32 and the weft yarns 33 respectively comprises numerouscontinuous carbon filaments. The first resin 34 adheres relatively moredensely on a surface of the fabric 35.

[0104]FIG. 4 is a typical vertical sectional view showing still furthermode of the carbon fiber reinforced substrate of the invention differentfrom the mode of FIG. 3. In FIG. 4, a carbon fiber reinforced substrate41 comprises a fabric 45 and a first resin 44 adhering to the fabric 45.The fabric 45 comprises warp yarns 42 formed by carbon fiber bundles andweft yarns 43 formed by auxiliary fiber bundles. The warp yarns 42 andthe weft yarns 43 form the fabric 45 in a plain weave. Since the fabric45 is mainly composed of the warp yarns 42 formed by carbon fiberbundles, it is a kind of unidirectional woven fabric. Each of the carbonfiber bundles used as the warp yarns 42 comprises numerous continuouscarbon filaments. The first resin 44 relatively more densely adheres toa surface of the fabric 45.

[0105] The first resin may adhere as dots on a surface of the fabric 15as shown as the first resin 14 in FIG. 1, or may adhere on a surface ofthe fabric 25 to more widely cover the surface than in FIG. 1 butdiscontinuously, as shown as the first resin 24 in FIG. 2.

[0106] The state in which the first resin 14 adheres as dots on asurface of the fabric 15 in FIG. 1 is also explained as follows. Thatis, in FIG. 1, if a surface of the fabric 15 is considered as the seawhile the first resin 14 is considered as islands, then the first resin14 existing on the surface of the fabric 15 shown in FIG. 1 can be saidto be a group of numerous small islands. The maximum width of the smallislands is smaller than the widths of the warp yarns 12 and the weftyarns 13.

[0107] The state in which the first resin 24 adheres on a surface of thefabric 25 discontinuously in FIG. 2 is also explained as follows. Thatis, in FIG. 2, if a surface of the fabric 25 is considered as the seawhile the first resin 24 is considered as islands in FIG. 2, then thefirst resin 24 existing on the surface of the fabric 25 shown in FIG. 2can be said to be a group of many large islands scattered in the sea.Some of the large islands contain lakes 26 in them. The minimum width ofthe large islands is larger than the width of each warp yarn 22, andsmaller than the total width of four warp yarns 22.

[0108] Though not illustrated, a figure of existing of the first resinmay also be a mixed state of the small islands shown in FIG. 1 and thelarge islands shown in FIG. 2.

[0109] It is not preferred that the first resin adheres to the fabric insuch a manner as to cover the fabric entirely like a film, since thepermeation (especially the permeation in the direction perpendicular tothe laminate surface) of the third resin described later into the carbonfiber reinforced substrates laminated is remarkably inhibited.Furthermore, it is not preferred either that the first resin can easilyabsorb water and adheres to the fabric in such a manner as to cover thefabric continuously not only as a film but also as filaments or anon-woven fabric, since where a formed composite is treated in hot-wetcondition, the water absorption effect extends in a wide range throughthe first resin.

[0110] Therefore, it is desirable that the first resin adheres like dotsor discontinuously. In the case where the first resin adheres on asurface of the fabric 15 like dots as shown in FIG. 1, if the averagediameter of the dots (islands) (the average minor axis if the dots areoval) is smaller, the dots can be dispersed more uniformly on thesurface of the fabric 15. So, it is desirable that the average diameteris 1 mm or less, more desirably 250 μm or less, and still more desirably50 μm or less.

[0111] In the case where plural layers of the carbon fiber reinforcedsubstrate having the first resin relatively more densely adhering to thesurfaces of the fabric layers are laminated, if the first resinrelatively more densely adhering on the surfaces of the fabric layers isexcessively rugged in the direction perpendicular to the surfaces of thesubstrate, the carbon fiber bundles located in contact with the firstresin are greatly deflected. In this case, the compression properties ofthe composite such as the compression strength at room temperature(hereinafter abbreviated as CS) and the compression strength at hightemperature after hot-wet conditioning (hereinafter abbreviated as CHW)may be impaired. On the other hand, if the amount of the first resin istoo small, the composite cannot have desired properties.

[0112] In view of the above, it is preferred that the average thicknessof the first resin on the surface of the fabric is in a range from 5 to250 μm. A more preferred range is from 10 to 100 μm, and a further morepreferred range is from 15 to 60 μ.

[0113] The amount of the first resin deposited on the fabric is in arange from 1 to 20 parts by weight per 100 parts by weight of thefabric. A preferred deposited amount range is from 1 to 10 parts byweight, and a more preferred range is from 3 to 7 parts by weight. Afurther more preferred range is from 4 to 6 parts by weight.

[0114] If the deposited amount of the first resin is less than 1 part byweight, the handling properties of the carbon fiber reinforced substratesuch as stiffness, form stability, drapability and tackiness inlamination become poor, and the effect of improving the mechanicalproperties of the composite is also small.

[0115] If the deposited amount of the first resin is more than 20 partsby weight, the composite obtained cannot be excellent in mechanicalproperties, especially in CHW, and carbon fiber content of the compositebecomes too low. Furthermore, it can happen that the permeation of thethird resin as the matrix resin described later into the carbon fiberreinforced substrate or into the preform may be prevented when thecomposite is produced. In the case where the deposited amount of thefirst resin is 10 parts by weight or less, since the preform in thecomposite can be made narrow in the interlayer space and smooth,compression properties such as CHW and CS can be more improved.

[0116] The fabric is composed of carbon fiber bundles. The fabric can bein any of various known forms such as a woven fabric (uni-directional,bi-directional or 3D woven fabric, etc.), knitted fabric, braid, fabricwith warp yarns (carbon fiber bundles) arranged in parallel to eachother in one direction (hereinafter called a uni-directional sheet),multi-axial sheet obtained by overlaying two or more uni-directionalsheet in different directions, etc. The fabric can also be an integralproduct comprising plural fabrics bonded by any of various binding meanssuch as stitch yarns, knot yarns or resin (porous film, nonwoven fabric,binder, etc.).

[0117] In the case where the composite is used as a structure element ofa transport machine, it is preferred that the fabric of the carbon fiberreinforced substrate is a uni-directional woven fabric, bi-directionalwoven fabric, uni-directional sheet or multi-axial fabric (especiallymulti-axial fabric bonded by stitch yarns).

[0118] A primary or principal structure element of an aircraft isrequired to have very high mechanical properties (especially CAI andCHW). In a bi-directional woven fabric, since the carbon fiber bundlesform a bi-directional weave structure, it can happen that the crimps ofthe carbon fiber bundles become large at the interlacing points betweenwarp yarns and weft yarns. In this case, it can happen that the firstresin 34 does not exist at interlacing points between the warp yarns 32and the weft yarns 33, though it exists in FIG. 3. In this case, themechanical properties may not be able to meet the requirement.

[0119] Therefore, to obtain more preferred mechanical properties, it ispreferred that the fabric is a uni-directional woven fabric or auni-directional sheet. Furthermore, considering the permeation of thematrix resin, especially preferred is a uni-directional woven fabric, inwhich small crimps formed by weft auxiliary yarns exist between warpyarns (carbon fiber bundles). The crimps are useful for forming thepassages for allowing the permeation of the matrix resin, to remarkablyenhance the matrix resin permeability of the preform.

[0120]FIG. 5 is a perspective view showing another mode (uni-directionalwoven fabric) of the fabric used in the carbon fiber reinforcedsubstrate of the invention. In FIG. 5, a uni-directional woven fabric 51is a plain weave, in which warp yarns 52 arranged in parallel to eachother in one direction and auxiliary weft yarns 53 perpendicular to thewarp yarns 52 interlace with each other. The warp yarns 52 are formed bycarbon fiber bundles, and the auxiliary weft yarns 53 are formed byauxiliary fiber bundles.

[0121] Each of the carbon fiber bundles forming the warp yarns 52 of theuni-directional woven fabric 51 comprises 5,000 to 50,000 continuouscarbon filaments. More preferred number of carbon filaments in eachcarbon fiber bundle is 10,000 to 25,000.

[0122] It is preferred that the fineness or titer of the warp yarns 52of the unidirectional woven fabric 51 is in a range from 300 to 5,000tex. If the fineness is less than 300 tex, the number of interlacingpoints between the warp yarns 52 and the auxiliary weft yarns 53 is toolarge. As a result, the crimps at the interlacing points become large,and the number of crimps also becomes large. In this case, it can happenthat the mechanical properties of the obtained composite become poor. Ifthe fineness is more than 5,000 tex, the number of interlacing points istoo small, and the form stability of the carbon fiber reinforcedsubstrate may become low.

[0123] It is preferred that the auxiliary fiber bundles forming theauxiliary weft yarns 53 are selected to ensure that the crimps of thewarp yarns 52 at the interlacing points between the warp yarns 52 andthe auxiliary weft yarns 53 become small. In this case, the propertiesof the carbon fiber bundles used as the warp yarns 52 can be exhibitedto the maximum possible extent.

[0124] It is preferred that the fineness of the auxiliary fiber bundlesforming the auxiliary weft yarns 53 is not more than ⅕ of the finenessof the carbon fiber bundles forming the warp yarns 52, more preferably{fraction (1/10)} or less. The particular fineness depends on the kindsof the carbon fiber bundles and auxiliary fiber bundles used and theunit weight of the woven fabric. For example, in the case where carbonfiber bundles of 800 tex are used to form a woven fabric with a unitweight of 200 g/m², it is preferred that the fineness of the auxiliaryfiber bundles is in a range from 10 to 100 tex, more preferably from 20to 50 tex.

[0125] It is preferred that the number of weft ends of the auxiliaryweft yarns 23 (FIG. 2) or the auxiliary weft yarns 53 (FIG. 5) is in arange from 0.3 to 6 ends/cm for stabilizing the form of the fabric andfor minimizing the influence of warp yarn crimps, more preferably from 1to 4 ends/cm.

[0126] For the auxiliary fiber bundles, any desired material can beused. However, in view of the stability of warp ends and weft ends, amaterial that is unlikely to be shrunken, for example, by the heatingfor molding is preferred. For example, carbon fibers, glass fibers,organic fibers such as aramid fibers, polyamide fibers (especially POY),PBO fibers, PVA fibers or PE fibers, or a combination thereof can beused. The fibers secondarily yarned, for example, doubled, twisted,wooly-treated or crimped can also be used.

[0127] Warp yarns, weft yarns and auxiliary weft yarns may also be usedin combination with an adhesive component for fixing the weavestructure. Examples of the adhesive component include thermoplasticresins such as nylon resins and polyester resins, thermosetting resinssuch as epoxy resins, unsaturated polyester resins and phenol resins,etc. The form of the adhesive component can be fibers, particles,emulsion or dispersion, etc. The adhesive component in any of theseforms may be combined with warp yarns, weft yarns or auxiliary weftyarns. Above all, if the adhesive component in the form of fibers istwisted together with the auxiliary fiber bundles or used as coveringyarns for covering the auxiliary fiber bundles, for use as auxiliaryweft yarns, the effect of fixing the weave structure is high.

[0128] The uni-directional woven fabric may be a plain weave shown inFIG. 5, or a twill weave or a satin weave. Furthermore, a woven fabricwith a non-crimp structure as shown in FIG. 6 may also be used.

[0129]FIG. 6 is a perspective view showing yet another mode(uni-directional woven fabric) of the fabric used in the carbon fiberreinforced substrate of the invention. In FIG. 6, a uni-directionalwoven fabric 61 comprises warp yarns 62 formed by carbon fiber bundles,auxiliary warp yarns 64 formed by auxiliary fiber bundles arranged inparallel with the warp yarns 62, and auxiliary weft yarns 63 formed byauxiliary fiber bundles arranged in the direction perpendicular to theyarns 62 and 64. The auxiliary warp yarns 64 and the auxiliary weftyarns 63 are interlaced with each other, to integrally hold the warpyarns 62 formed by carbon fiber bundles, for forming the woven fabric(woven fabric having a non-crimp structure) 61.

[0130] The woven fabric (woven fabric having a non-crimp structure) 61has further smaller crimps than the uni-directional woven fabric 51 witha plain weave shown in FIG. 5. So, the composite produced by the wovenfabric can more highly exhibit the properties of the carbon fiberbundles. Furthermore, also in view of matrix resin permeation, since theauxiliary fiber bundles provide resin permeation passages, thepermeability is very excellent.

[0131] In the case where the fabric is a bi-directional woven fabric,uni-directional woven fabric or uni-directional sheet, in view of thepermeation of the third resin described later into the carbon fiberreinforced substrate or into the preform and the mechanical propertiesof the composite, it is preferred that the carbon fiber unit weight ofthe carbon fiber reinforced substrate, i.e., the carbon fiber unitweight of the fabric is in a range from 50 to 500 g/m², more preferablyfrom 100 to 350 g/m², and still more preferably from 150 to 250 g/m². Itis preferred that the thickness of the carbon fiber reinforced substrateis in a range from 0.1 to 0.8 mm, more preferably from 0.15 to 0.7 mm,and still more preferably from 0.2 to 0.6 mm.

[0132] In the case where the fabric is a multi-axial fabric, it ispreferred that the carbon fiber unit weight of the carbon fiberreinforced substrate is in a range from 150 to 1500 g/m², morepreferably from 300 to 1000 g/m², and still more preferably from 400 to800 g/m². The reasons why the carbon fiber unit weight of a multi-axialfabric can be larger than that of a uni-directional woven fabric or thelike are that especially in the case where stitch yarns or the likeexist in the thickness direction, the resin paths in the thicknessdirection can be secured, to allow easier resin permeation, and that ifthe unit weight is small, it is not necessary to have a multi-layerfabric.

[0133] In view of resin permeability, it is preferred that the airpermeability of the carbon fiber reinforced substrate is in a range from10 to 200 cm³/cm²·sec, more preferably from 12 to 120 cm³/cm²·sec, andstill more preferably from 15 to 100 cm³/cm²·sec.

[0134] If the air permeability is less than 10 cm³/cm²·sec, the resinpermeability is too low. An air permeability of more than 200cm³/cm²·sec is not preferred, since the voids in the fabric become toolarge though the resin permeability is excellent, and since thecomposite obtained has many resin-rich portions formed, the lowering ofmechanical properties, thermal cracking and the like occur.

[0135] The air permeability is expressed as the amount of air permeatingthe fabric measured according to the method A described in JIS-L-1096(Frazier type). The value of air permeability in the specification ismeasured by AP-360 produced by K. K. Daiei Kagakuseiki Seisakusho.

[0136] In order to minimize the coming-off of the first resin from thefabric when the fabric is coated with the first resin and also in orderto exhibit the properties of the carbon fiber bundles per se to themaximum extent, it is preferred that the cover factor of the fabric is90% or more. It is more preferable the cover factor of the fabric is 97%or more, and still more preferable 99% or more.

[0137] The cover factor refers to the percentage of the closed (covered)portions where the carbon fibers (auxiliary yarns, stitch yarns, knotyarns and the like as the case may be) exist in the fabric per unit areaof 100 mm×100 mm when the planar fabric is observed in the directionperpendicular to it. The cover factor (%) is calculated from thefollowing equation: Cover factor (%)=Total area (mm²) of closedportions/10,000. In the case where the carbon fiber reinforced substrateis used for measuring the cover factor, the portions closed by the firstresin are not included. That is, the cover factor of the fabric can beconsidered to be the same as the cover factor of the carbon fiberreinforced substrate.

[0138] This measurement is carried out at least five times at optionalplaces of the fabric. The value of cover factor is the average value ofthese measured values. The total area of the closed portions iscalculated by means of image processing based on the image opticallypicked up by a CCD camera or scanner, etc.

[0139] A fabric having a cover factor of 90% or more is, for example, afabric formed by carbon fiber bundles respectively having a width of 4mm or more and flat in cross sectional form (a fabric comprising flatcarbon fiber bundles). It is preferred that the width of each carbonfiber bundle is 5 mm or more, more preferably 6 mm or more.

[0140] It is preferred that the flat carbon fiber fabric is spread bymeans of compressed air, roller or indenter, etc. The reason is that thespreading can reduce the thickness of the fabric and enhance the carbonfiber content in the composite. The flat carbon fiber fabric (wovenfabric) per se is disclosed in more detail in JP 2955145 and JP 11-1840A. It is preferred that the carbon fiber bundles are substantially nottwisted in view of matrix resin permeability and the exhibition ofmechanical properties.

[0141] It is preferred that the first resin has a melting point or flowinitiation temperature of 50 to 150° C. in view of the temperature usedfor obtaining the tackiness necessary for laminating layers of thecarbon fiber reinforced substrate. It is more preferred that the meltingpoint or flow initiation temperature is in a range from 70 to 140° C.,still more preferably from 90 to 120° C.

[0142] For a resin showing a melting point, the melting point refers tothe temperature measured using a differential scanning calorimeter(DSC), at which the resin is molten. For a resin not showing a meltingpoint, the flow initiation temperature refers to the temperaturemeasured by means of viscoelasticity measurement (Flow Tester CFT 500Dproduced by Shimadzu Corp, heating rate 1.5° C./min), at which the resinbegins flowing.

[0143] It is preferred that the water absorption coefficient(equilibrium water absorption coefficient) of the first resin at 23° C.and 50% RH is 3 wt % or less. It is more preferable that the waterabsorption is 2.2 wt % or less, still more preferably 1.8 wt % or less,further more preferably 1.4 wt % or less.

[0144] If the equilibrium water absorption coefficient is more than 3 wt%, a composite with excellent mechanical properties (especially CHW) maynot be obtained. The equilibrium water absorption coefficient ismeasured according to the method described in ASTM-D-570.

[0145] The first resin is not especially limited, if it can improve thehandling properties of the carbon fiber reinforced substrate and improvethe mechanical properties of the composite obtained by using the carbonfiber reinforced substrate. As the first resin, a thermosetting resinand/or a thermoplastic resin may be adequately selectively used.

[0146] Examples of the thermosetting resin include epoxy resins, phenolresins, polybenzoimidazole resins, benzoxazine resins, cyanate esterresins, unsaturated polyester resins, vinyl ester resins, urea resins,melamine resins, bismaleimide resins, polyimide resins andpolyamideimide resins, their copolymers and modification products,resins obtained by blending two or more of the foregoing, and resinscontaining an elastomer, rubber component, curing agent, curingaccelerator, catalyst or the like.

[0147] Examples of the thermoplastic resin include polyester resins,polyolefin resins, styrene-based resins, polyoxymethylene resin,polyamide resins, polyurethane resins, polyurea resins,polydicyclopentadidene resin, polycarbonate resins, polymethylenemethacrylate resin, polyetherimide resins, polysulfone resins,polyallylate resins, polyether sulfone resins, polyketone resins,polyether ketone resins, polyether ether ketone resins, polyether ketoneketone resins, polyarylate resins, polyether nitrile resins, polyimideresins, polyamideimide resins, phenol resins, phenoxy resins,fluorine-based resins such as polytetrafluoroethylene resin, elastomers(preferably butadiene acrylonitrile, its carboxylic acid or aminemodification products, fluoroelastomers, polysiloxane elastomers),rubbers (butadiene, styrene butadiene, styrene butadiene styrene,styrene isoprene styrene, natural rubber, etc.), resins for RIM (e.g.,those containing a catalyst or the like capable of forming polyamide 6,polyamide 12, polyurethane, polyurea or polycicyclopentadiene), cyclicoligomers (those containing a catalyst or the like capable of forming apolycarbonate resin, polybutylene terephthalate resin, etc.), thecopolymers and modification products thereof, resins obtained byblending two or more of the foregoing, etc.

[0148] In the case where a thermosetting resin is used as the maincomponent of the first resin, at least one selected from the groupconsisting of epoxy resins, unsaturated polyester resins and phenolresins is preferred. Above all, an epoxy resin is especially preferred.If an epoxy resin is used, the handling properties of the substrate areexcellent since the adhesiveness is high, and especially in the casewhere an epoxy resin is used as the third resin described later, highmechanical properties can be preferably exhibited.

[0149] In the case where an epoxy resin is used as the main component ofthe first resin, it may, or is not required to, contain a curing agent,curing catalyst or the like. In view of the life of the first resin, thelatter is preferred. Even in the former case, a highly latent curingagent or curing catalyst does not pose any large problem.

[0150] In the case where a thermoplastic resin is used as the maincomponent of the first resin, at least one selected from the groupconsisting of polyamide resins, polysulfone resins, polyether sulfoneresins, polyetherimide resins, polyphenylene ether resins, polyimideresins, polyamideimide resins and phenoxy resins is preferred. Amongthem, polyamide resins, polyetherimide resins, polyphenylene etherresins, polyether sulfone resins and phenoxy resins are especiallypreferred.

[0151] It is preferred that a thermoplastic resin is the main componentof the first resin, and that its content is in a range from 70 to 100 wt%. A more preferred range is 75 to 97 wt %, and a further more preferredrange is 80 to 95 wt %. If the content is less than 70 wt %, it may bedifficult to obtain a composite with excellent mechanical properties.In. the case where a thermoplastic resin is used as the main component,it may happen that the adhesiveness of the first resin to the fabric orthe possibility of making the first resin adhesive to the fabric becomeslow. In this case, it is desirable to add a small amount of a tackifier,plasticizer or the like to the first resin.

[0152] In the carbon fiber reinforced substrate, it is preferred that asecond resin higher than the first resin in melting point or flowinitiation temperature adheres to the fabric, in addition to the firstresin. It is preferred that the amount of the second resin adhering tothe fabric is in a range from 1 to 10 parts by weight per 100 parts byweight of the fabric. In this case, the mechanical properties(especially CAI and CHW) can be further highly exhibited. It ispreferred that the second resin has a melting point or flow initiationtemperature of 150° C. or higher. It is more preferred that the meltingpoint or flow initiation temperature is 180° C. or higher, and furthermore preferred is 210° C. or higher.

[0153] It is only required that the second resin is not molten or doesnot flow at the melting point or flow initiation temperature of thefirst resin. A resin having neither a melting point nor a flowinitiation temperature, that is, a resin capable of being decomposedbefore being molten or before beginning to flow can also be used as thesecond resin.

[0154] If the second resin adheres to the fabric in addition to thefirst resin, preferably if these resins relatively more densely adhereon a surface of the fabric, the toughening effect and the interlaminartoughening effect can be more highly exhibited compared with the casewhere the first resin only adheres to the fabric, and as a result, themechanical properties (especially CAI) of the composite obtained bylaminating layers of the carbon fiber reinforced substrate can beremarkably improved.

[0155] The reason why the second resin can more highly exhibit theeffects than the first resin is that the second resin has a meltingpoint or flow initiation temperature higher than that of the firstresin, or that the second resin is not molten or does not flow at thetemperature at which the first resin is molten or begins to flow. Inaddition, since the adhesive first resin already exists, the secondresin per se is not absolutely required to be adhesive, and a highlytough but non-adhesive resin or a resin incapable of contributing toimproving the handling properties of the substrate can also be used. So,the second resin can be selected from a considerably wide range ofresins in terms of material and form than the first resin.

[0156] Considering the above-mentioned mechanisms, if a resin thatbecomes adhesive at a relatively low temperature and does not lower themechanical properties (preferably improves the mechanical properties) isused as the first resin while a resin capable of more highly exhibitingthe mechanical properties is used as the second resin adhering to thedry fabric, a more preferred carbon fiber substrate can be obtained.

[0157] The second resin may adhere in the inside of the fabric oradheres relatively more densely on a surface of the fabric, but forefficiently exhibiting the effects, it is preferred that the secondresin relatively more densely adheres substantially on a surface of thefabric like the first resin.

[0158] It is preferred that the amount of the second resin deposited onthe fabric is in a range from 1 to 10 parts by weight per 100 parts byweight of the fabric. It is more preferred that the deposited amount isin a range from 2 to 9 parts by weight per 100 parts by weight of thefabric. A further more preferred range is 3 to 7 parts by weight, and anespecially preferred range is 4 to 6 parts by weight.

[0159] If the deposited amount of the second resin is less than 1 partby weight, the effect of improving mechanical properties may be small.If the deposited amount of the second resin is more than 10 parts byweight, it can happen that the composite obtained is not especiallyexcellent in CHW after hot-wet conditioning, and the carbon fibercontent of the composite is too small. In addition, when the compositeis obtained, the permeation of the third resin described later as thematrix resin into the carbon fiber reinforced substrate may beprevented.

[0160] Meaning of using of the second resin is explained moreparticularly in reference to drawings.

[0161]FIG. 7 is a typical vertical sectional view showing still furthermode of the carbon fiber reinforced substrate of the invention. In FIG.7, a carbon fiber reinforced substrate 71 comprises a fabric(bi-directional woven fabric) 76 comprising warp yarns 72 formed bycarbon fiber bundles and weft yarns 73 formed by carbon fiber bundles,and a first resin 74 and a second resin 75 respectively adhering to thefabric 76. In the carbon fiber reinforced substrate 71, the second resin75 adheres to the fabric in addition to the first resin 74, unlike thecarbon fiber reinforced substrate 31 of FIG. 3. The second resin 75adheres as particles relatively more densely on a surface of the fabric76.

[0162]FIG. 8 is a typical vertical sectional view showing a stillfurther mode of the carbon fiber reinforced substrate of the inventiondifferent from the mode of FIG. 7. In FIG. 8, a carbon fiber reinforcedsubstrate 81 comprises a fabric (uni-directional woven fabric) 86consisting of warp yarns 82 formed by carbon fiber bundles and auxiliaryweft yarns 83 formed by auxiliary fiber bundles, and a first resin 84and a second resin 85 respectively adhering to the fabric 86. In thecarbon fiber reinforced substrate 81, the second resin 85 adheres to thefabric in addition to the first resin 84, unlike the carbon fiberreinforced substrate 41 of FIG. 4. The second resin 85 adheres asparticles relatively more densely on a surface of the fabric 86.

[0163] The second resin may adhere to the fabric by means of the firstresin or may independently adhere to the fabric, but it is preferredthat the second resin adheres to the fabric by means of the first resin.That is, the second resin can adhere to the fabric as integrated withthe first resin or can independently adhere to the fabric without beingintegrated with the first resin. However, it is preferred that thesecond resin is integrated with the first resin as in the former case.

[0164] If the second resin is integrated with the first resin, it canreliably adhere on a surface of the fabric. Furthermore, if the secondresin per se is made to directly adhere to the fabric, a temperaturehigher than the temperature used for making the first resin adhere isneeded. On the contrary, if the second resin is made to adhere to thefabric by means of the first resin, the second resin can be made toadhere to the fabric at a lower temperature.

[0165] As a result, the production efficiency of the carbon fiberreinforced substrate can be enhanced. Furthermore, the second resin isnot required to be adhesive. So, the second resin may be selected from awider range of resins, and a resin capable of more highly exhibiting themechanical properties can be selected.

[0166] Being integrated means that both the resins are not separatedfrom each other. For example, a mere dry blend consisting of particlesof the first resin and particles of the second resin cannot be referredto as an integrated state, since the respective resins are separate fromeach other.

[0167] In the case where the second resin integrated with the firstresin adheres, if the second resin is not substantially compatible lowith the first resin, the chemical reactivity between the first resinand the second resin can be minimized. So, even if the first resin andthe second resin are molten and mixed for integration, the rise ofviscosity can be prevented to the maximum extent. Furthermore, since theselectable range of resins in terms of material and form for the secondresin is less limited, the selectable range can be widened, and themechanical properties (especially CAI) of the obtained composite can befurther improved advantageously. From these points of view, it ispreferred that the second resin is not substantially compatible with thefirst resin.

[0168] In the case where the first resin and the second resin areintegrated with each other, it is preferred that the surfaces of thesecond resin particles are partially (preferably 50% or more of thetotal surface area, more preferably 90% or more) covered with the firstresin. If the first resin and the second resin in this state adhere tothe fabric, the second resin can be made to adhere to the fabric bymeans of the first resin more reliably compared with a case where a meredry blend consisting of the first resin and the second resin (notintegrated) is used.

[0169] For integrating the first resin and the second resin, both theresins can be molten and mixed for obtaining a mixture with a desiredmode. As another method, both the resins can be mixed using a solventcapable of dissolving them, and the solvent can be removed for obtaininga mixture with a desired mode. In view of working environment, meltmixing is preferred. For melt mixing, an adequate apparatus such as asingle-screw extruder, double-screw extruder, Banbury mixer, kneader orthree-roll mill can be selectively used.

[0170] The form of the second resin is not especially limited, and anydesired form, for example, a fabric such as a woven fabric, knittedfabric, nonwoven fabric or mattress, particles, discontinuous pieces orany combination of the foregoing can be employed. It is preferred toselect a form suitable for the purpose of the composite, but in view ofmicroscopic homogeneity, mechanical property improving effect andinhibition of water absorption, a form of particles (preferablyspherical) or discontinuous pieces is most preferred.

[0171] In the case where the second resin has a form of particles, it ispreferred that the average particle diameter is in a range from 1 to 500μm, in order to uniformly disperse the particles on a surface of thefabric. A more preferred average particle diameter range is from 1 to150 μm, and a further more preferred range is 3 to 100 μm. If theaverage particle diameter is less than 1 μm, more particles enter intothe clearances between the carbon filaments of the carbon fiber bundlesconstituting the fabric, and the amount of the particles adhering on thesurface becomes small. If the average particle diameter is more than 150μm, the number of the particles made to adhere per a predeterminedweight of scattered particles becomes small since the particle diameterbecomes large, and it may be difficult to scatter uniformly. The averageparticle diameter refers to the D₅₀ measured by the laser-diffractionscattering method. For the measurement, LMS-24 produced by SeishinEnterprise Co., Ltd. is used.

[0172] It is preferred that the water absorption coefficient of thesecond resin at 23° C. and 50 RH is 2.5 wt % or less. A more preferredwater absorption coefficient is 1.8 wt %, and a further more preferredwater absorption coefficient is 1.5 wt % or less. An especiallypreferred water absorption coefficient is 1.1 wt % or less. If the waterabsorption coefficient is more than 2.5 wt %, the composite obtained maynot be excellent in mechanical properties (especially CHW). The waterabsorption coefficient refers to the value measured according toASTM-D-570.

[0173] The second resin is not especially limited either like the firstresin, if it is a resin capable of solving the problems of theinvention. It is preferred that the main component of the second resinis a highly tough thermoplastic resin, and can be selected from theabove-enumerated examples of the first resin. Above all, it is desirableto use at least one selected from the group consisting of polyamideresins, polyimide resins, polyamideimide resins, polyetherimide resins,polysulfone resins, polyether sulfone resins, polyphenylene etherresins, polyether ether ketone resins and polyether ketone ketoneresins. Especially at least one selected from the group consisting ofpolyamide resins, polyamideimide resins, polyetherimide resins andpolyether sulfone resins can easily exhibit the above-mentioned effects.

[0174] In the case where a polyamide is used as the main component ofthe second resin, it is preferred to use a homopolyamide such aspolyamide 6, polyamide 66, polyamide 12, polyamide 610, polyamide 612,aromatic dicarboxylic acid or diamine such as isophthalic acid,terephthalic acid, paraxylenediamine or metaxylenediamine, alicyclicdicarboxylic acid or diamine such asdimethylbis(p-aminocyclohexyl)methane, or a copolyamide consisting oftwo or more of the foregoing.

[0175] Commercially available polyamides suitable for the second resininclude Transparent Nylon T-714E, T-714H and T-600 respectively producedby Toyobo Co., Ltd., Trogamid T5000 and CX7323 respectively produced byDaicelhuls Ltd., Grilamid TR55 and TR90 respectively produced byEMS-Chemie, SP500 (particles) produced by Toray Industries, Inc.,Genestar PA-9T produced by Kuraray Co., Ltd., etc.

[0176] It is preferred that the glass transition temperature of thepolyamide measured by DSC is 100° C. or higher. More preferred is 125°C. or higher, and further more preferred is 150° C. or higher. Thepreferred polyamide has sufficient heat resistance when the composite isproduced by molding, and can further enhance the effects (especiallyCAI) of using the second resin. In the meantime, for example, polyamide12 exhibits a high effect of improving CAI, though it has a glasstransition temperature of lower than 100° C. That is, it is preferredthat a polyamide having a melting point has a glass transitiontemperature in a range from 30° C. to 280° C.

[0177] In the case where a thermoplastic resin is used as the secondresin, if a thermosetting resin such as an epoxy resin is used as thefirst resin for making both the first resin and the second resin adhereintegrally, both CAI and CHW can be enhanced to high levels.Furthermore, if a thermoplastic resin with a low melting point such as apolyamide resin with a low melting point is used as the first resin formaking both the resins adhere integrally, CAI can be enhanced to anespecially high level.

[0178] It is preferred that the second resin contains a thermosettingresin as a subsidiary component that can be selected from theabove-enumerated examples of the first resin. Among them, an epoxy resinor phenol resin is preferred. If the subsidiary component covers themain component of the second resin or is at least partially (preferablywholly) converted to form a polymer alloy {preferably aninterpenetrating polymer network (IPN)}, the chemical interaction withthe third resin described later can be controlled. As a result, theabove-mentioned effects (especially CAI) of using the second resin canbe further enhanced. It exhibits preferred effects also in improving thechemicals resistance and heat resistance of the second resin and ininhibiting water absorption.

[0179] These effects can be especially remarkably exhibited in the casewhere a thermoplastic resin (especially a polyamide resin) is used asthe second resin. In the case where a thermosetting resin is containedas a subsidiary component (especially when IPN is formed), it can happenthat the second resin has neither the melting point nor the flowinitiation temperature, but it is only required that the second resin isnot molten or caused to flow at the melting point or flow initiationtemperature of the first resin.

[0180] The preform of the invention has at least two layers of theabove-mentioned carbon fiber reinforced substrate laminated, in whichthe layers of the carbon fiber reinforced substrate are integrallybonded by means of the first resin or the second resin.

[0181] If the bonding prevails on the entire surfaces of the carbonfiber reinforced substrate layers, it can happen that the handlingproperties of the preform become poor, and that the matrix resinpermeation is prevented. The bonding is only required to be such thatthe laminated plural carbon fiber reinforced substrate layers can behandled integrally, and it is preferred that the substrate layers arepartially bonded to each other.

[0182] Instead of laminating layers of a carbon fiber reinforcedsubstrate, carbon fiber reinforced substrates different in the amount ofthe first resin or the second resin adhering to the fabric may also belaminated. Especially in the case of a preform produced by the RTMprocess using a male mold half and a female mold half, or in the case ofa preform used for vacuum molding, in which a cavity formed by either amale mold half or a female mold half and a bag material is reduced inpressure to allow resin injection using the pressure difference betweenthe reduced pressure and the atmospheric pressure, if carbon fibersubstrates different in the amount of the first resin or the secondresin adhering to the fabric are positively used, the passages of thethird resin described later can be secured and controlled.

[0183] This is explained more particularly in reference to a drawing.FIG. 9 is a typical vertical sectional view showing a mode of thepreform of the invention. In FIG. 9, a carbon fiber reinforced substrate90 of the invention, in which a first resin 93 and a second resin 94relatively more densely adhering on the surfaces of respective fabrics92 consisting of carbon fiber bundles, is a laminate consisting of fourlayers. The four layers of the carbon fiber reinforced substrate 90 arebonded to each other by means of the first resin 93 or the second resin94, to form a preform 91. The preform 91 is a dry preform, in which thefour layers of the carbon fiber reinforced substrate 90 are integrated,and the bulk volume fraction of fibers is minimized owing to theinterlaminar bonding by means of the first resin 93 or the second resin94. Therefore, the preform 91 is excellent in handling properties.

[0184] The composite of the invention is obtained by a method ofimpregnating the formed preform with a third resin used as a matrixresin different from the first resin, and subsequently solidifying theresin. The third resin permeated into the preform is solidified (curedor polymerized). The solidification of the third resin results informing the composite.

[0185] This is explained more particularly in reference to a drawing.FIG. 10 is a typical vertical sectional view showing a mode of thecomposite of the invention. In FIG. 10, the clearances between thelayers of the carbon fiber reinforced substrate 90 laminated in thepreform 91 shown in FIG. 9 are impregnated with a third resin 102 thatis then cured or polymerized for solidification to form a composite 101.

[0186] The third resin 102 is not especially limited like the firstresin 93, if it is a resin capable of solving the problems of theinvention, but a thermosetting resin is preferred in view of moldabilityand mechanical properties. It can be selected from the above-enumeratedexamples of the first resin. However, unlike the first resin, in thecase where injection molding is used, the third resin must be a liquidat the injection temperature.

[0187] It is preferred that the thermosetting resin as the third resinis at least one selected from the group consisting of epoxy resins,phenol resins, vinyl ester resins, unsaturated polyester resins, cyanateester resins, bismaleimide resins and benzoxazine resins, since theproblems of this invention can be easily solved. Furthermore, resinscontaining an elastomer, rubber, curing gent, curing accelerator,catalyst or the like can also be used. Above all, to achieve, forexample, very high mechanical properties (especially CAI and CHW)required for primary or principal structure elements of aircraft, anepoxy resin or bismaleimide resin is preferred. Especially an epoxyresin is preferred.

[0188] Since the third resin and the first resin are used respectivelyfor different functions, it is desirable to use resins at leastpartially different from each other. That is, it is preferred to use arein excellent in permeability (having a low viscosity at the injectiontemperature and a long gelation time) and excellent in mechanicalproperties as the third resin, and to use a resin capable of improvingthe handling properties of the fabric and imparting high mechanicalproperties as the first resin. Of course, the first resin and the thirdresin can contain a component common to them without any problem, and itmay be preferred in view of the compatibility between both.

[0189] In the case where the third resin 102 is impregnated into thepreform 91 in the injection or infusion molding described later, if thethird resin has a low viscosity, the molding cycle can be shortenedsince the resin can be easily impregnated. It is preferred that theviscosity at the injection temperature is 400 mpa.s or less. Morepreferred is 200 mPa.s or less. It is preferred that the injectiontemperature is 100° C. or lower, since simple equipment can be used.

[0190] The composite can be obtained by any of various molding methodssuch as injection or infusion molding (TRM, RFI, RIM, vacuum molding,etc.) and press molding, or a combination of such molding methods.

[0191] A more preferred molding method for obtaining the composite is aninjection molding method with high productivity such as RTM. In one ofRTM methods, a resin is injected under pressurization into a cavityformed by a male mold half and a female mold half. In this case, it ispreferred that the cavity is reduced in pressure for resin injection.Another preferred molding method is a vacuum molding method. In vacuummolding, for example, a cavity formed by either a male mold half or afemale mold half and a bag material such as a film, particularly, anylon film, silicone rubber or the like, is reduced in pressure, and thepressure difference between the reduced pressure and the atmosphericpressure is used for injecting a resin. In this case, it is preferred todispose a resin distribution medium on the preform in the cavity foraccelerating resin permeation, and to separate the medium from thecomposite after completion of molding. These particular molding methodscan be used preferably in view of molding cost.

[0192] The applications of the composite of the invention are notespecially limited. Since the composite has excellent mechanicalproperties (especially CAI and CHW), it exhibits its effects to themaximum extent, if it is used as a primary or principle structureelement, secondary structure element, exterior element, interior elementor any of parts thereof in transport machines such as aircrafts, motorvehicles and ships.

[0193]FIG. 11 is a schematic perspective view showing primary structureelements of an aircraft. In FIG. 11, an airplane 111 consists of variousstructure elements such as main wings 112, keel beams 113, fuselage 114,vertical fin 115 and horizontal stabilizers 116. If the compositeobtained by a method of impregnating a preform composed of the carbonfiber reinforced substrate of the invention with a matrix resin andmolding it is used, a structure element having excellent mechanicalproperties (especially CAI and CHW) can be produced at highproductivity.

[0194]FIG. 12 is a schematic perspective view showing an example of astructural element in which the composite of the invention is applied.FIG. 13 is a schematic perspective view showing another example of astructural element in which the composite of the invention is applied.In FIG. 12, a structure element 121 is composed of skins 122, beams 123and ribs 124. In FIG. 13, a structure element 131 is composed of skins132, beams 133 and ribs 134. In conventional structure elements, theskins 122 and 132, spars 123 and 133 and stiffeners 124 and 134 arerespectively molded separately, and they are joined by means of rivetsor adhesive, to produce the intended structure elements. However, in thecomposite of the invention, the skins, beams and ribs can be integrallymolded, to greatly reduce the molding cost of structure elements.

[0195] The invention will be explained further with examples. In theexamples, the following raw materials were used.

[0196] Carbon fiber bundles A: PAN-system carbon fibers, each bundleconsisting of 24,000 filaments, and having a fineness of 1,000 tex, atensile strength of 5830 MPa, a tensile modulus of 294 GPa and afracture strain energy of 58 MJ/m³.

[0197] Carbon fiber bundles B: PAN-system carbon fibers, each bundleconsisting of 12,000 filaments, and having a fineness of 800 tex, atensile strength of 4,900 MPa, a tensile modulus of 235 GPa and afracture strain energy of 52 MJ/m³.

[0198] Carbon fiber bundles C: PAN-system carbon fibers, each bundleconsisting of 6,006 filaments, and having a fineness of 396 tex, atensile strength of 3,530 MPa, a tensile modulus of 235 GPa and afracture strain energy of 27 MJ/m³.

[0199] Glass fiber bundles: ECE225 1/0 1Z, each bundle having a finenessof 22.5 tex and using type “DP” binder (produced by Nitto Bouseki Co.,Ltd.).

[0200] First resin A: A resin composition obtained by hotmelt-kneading60 wt % of a polyether sulfone resin (finely ground “Sumika Excel” 5003Pproduced by Sumitomo Chemical Co., Ltd.) and 40 wt % of an epoxy resin(AK-601 produced by Nippon Kayaku Co., Ltd.) using a double-screwextruder, having a glass transition temperature of 75° C.

[0201] First resin B: An epoxy resin (“Epikote” 1004AF produced by JapanEpoxy Resin Co., Ltd.), having a flow initiation temperature of 100° C.

[0202] First resin C: An epoxy resin (PT500 produced by 3M).

[0203] Second resin: Spherical particles obtained by converting 90 wt %of a polyamide resin (“Grilamide” TR55 produced by EMS-Showa Denko K.K.,having a glass transition temperature of 162° C.) and 10 wt % of anepoxy resin and a curing agent into a polymer alloy (IPN). Averageparticle size (D₅₀) measured by the laser-diffraction scattering methodis 13 μm.

[0204] Third resin: A liquid epoxy resin composition obtained by adding32 parts by weight of the following curing solution to 100 parts byweight of the following main solution preheated to 70° C. and stirringtill the mixture became homogeneous. The viscosity at 70° C. measuredusing Model E viscometer is 250 mPa.s.

[0205] Main solution: 30 parts by weight of “Araldite(R)” MY-721produced by Vantico Inc., 20 parts by weight of “Epikote” 825 producedby Japan Epoxy Resins Co., Ltd., 20 parts by weight of AK-601 producedby Nippon Kayaku Co., Ltd., 30 parts by weight of “Epiclon(R)” HP-7200Lproduced by Dainippon Ink and Chemicals, Inc., and 1.4 parts by weightof n-propyl p-toluenesulfonate as a curing accelerator were respectivelyweighed and stirred at 100° C., till the mixture became homogeneous.

[0206] Curing solution: 18.1 parts by weight of “Epikure” W produced byJapan Epoxy Resins Co., Ltd. as an aromatic polyamine, 7.2 parts byweight of 3,3′-diaminodiphenylsulfone produced by Mitsui Kagaku FineChemicals, Inc. and 7.2 parts by weight of “Sumicure” S produced bySumitomo Chemical Co., Ltd. were respectively weighed and stirred at 90°C., till the mixture became homogeneous.

EXAMPLE 1

[0207] The first resin A was freeze-crushed into particles. The averageparticle size D₅₀ of the particles was 124 μm.

[0208] Using the carbon fiber bundles A as warp yarns and glass fiberbundles as auxiliary weft yarns, a uni-directional woven fabric A wasformed. The woven fabric A was a plain weave, and had a thickness of 0.3mm, a carbon fiber unit weight of 295 g/m², 2.8 warp ends/cm and 3 weftends/cm. The obtained uni-directional woven fabric A was 3.5 mm in thewidth of each carbon fiber bundle used as a warp yarn and more than 10in the ratio of the width to the thickness of the carbon fiber bundle,and was a flat woven fabric. Before weaving, each of the carbon fiberbundles A had a width of 5.8 mm and a thickness of 0.15 mm.

[0209] The particles of the first resin A were allowed to naturally dropto coat the obtained uni-directional woven fabric A through a vibrationnet for uniform dispersion, while they were weighed using an emboss rolland a doctor blade. In this coating, 100 parts by weight of the wovenfabric were coated with 10 parts by weight of the first resin.Furthermore, while the coated fabric was heated in a range from 180 to200° C. using a far infrared heater, metallic touch rollers treated toallow releasing were used to pressurize the fabric, for letting theparticles of the first resin A adhere to the uni-directional wovenfabric A, which was then cooled and taken up as a carbon fiberreinforced substrate A. In this example, the process from the weavingstep including a weaving machine to the cooling step was carried out inthe same line continuously. The obtained carbon fiber reinforcedsubstrate A had a thickness of 0.36 mm, an air permeability of 23.7cm³/cm²·sec, and a cover factor of 99%.

EXAMPLE 2

[0210] Fifty parts by weight of the first resin B and 50 parts by weightof the second resin were melt-kneaded at 170° C. using a kneader, andfreeze-ground, to obtain particles consisting of both the resinsintegrated. The average particle diameter D₅₀ of the particles was 38μm. The second resin was not molten or did not flow at the flowinitiation temperature of the first resin B, and both the resins werenot compatible with each other.

[0211] The obtained particles were electrically charged using“Tricomatic (R)” II powder coating system produced by NordsonCorporation, while being uniformly dispersed by means of compressed air,to be applied to the uni-directional woven fabric A obtained asdescribed in Example 1. In this coating, 100 parts by weight of thewoven fabric were coated with 14 parts by weight of the particles.Furthermore, the coated fabric was heated in a range from 140 to 160°C., using a hot press roller, for letting the particles adhere to theuni-directional woven fabric A, which was then cooled and taken up as acarbon fiber reinforced substrate B. In this example, the process fromthe weaving step to the coating, bonding and cooling steps was carriedout in different lines discontinuously. The particles were moreuniformly dispersed on the uni-directional woven fabric A than those ofExample 1, showing that the coating and bonding methods of Example 2were more excellent than those of Example 1.

EXAMPLE 3

[0212] The carbon fiber bundles A were used as warp yarns, and glassfiber bundles were respectively covered with a nylon yarn with a lowmelting point (“Elder” produced by Toray Industries, Inc., 6 tex) foruse as auxiliary weft yarns, to form a uni-directional woven fabric C.The woven fabric C was a plain weave, and had a thickness of 0.26 mm, acarbon fiber unit weight of 193 g/m², 1.8 warp ends/cm and 3 weftends/cm. The woven fabric C was 5.5 mm in the width of each carbon fiberbundle used as a warp yarn and more than 20 in the ratio of the width tothe thickness of the carbon fiber bundle, and was a woven fabric flatterthan the uni-directional woven fabric A of Example 1. A carbon fiberreinforced substrate C was obtained as described for Example 1, exceptthat the woven fabric C was used and that 100 parts by weight of thewoven fabric C were coated with 14 parts by weight of the first resin A.The obtained carbon fiber reinforced substrate C had a thickness of 0.37mm, an air permeability of 72.0 cm³/cm²·sec, and a cover factor of 93%.

EXAMPLE 4

[0213] A bi-directional woven fabric D was woven using the carbon fiberbundles B as warp yarns and weft yarns. The woven fabric D was a plainweave, and had a thickness of 0.19 mm, a carbon fiber unit weight of19.3 g/m², 1.21 warp ends/cm, and 1.21 warp ends/cm. A carbon fiberreinforced substrate D was obtained as described for Example 1, exceptthat the woven fabric D was used and that 100 parts by weight of thewoven fabric D were coated with 5 parts by weight of the first resin A.The obtained carbon fiber reinforced substrate D had a thickness of 0.24mm, an air permeability of 15.6 cm³/cm²·sec, and a cover factor of 99%.

EXAMPLE 5

[0214] The carbon fiber reinforced substrate A and the carbon fiberreinforced substrate B were respectively cut to have a length of 340 mmand a width of 340 mm. For each substrate, a stack architecture of[−45°/0°/+45°/90°] was repeated twice to form a set, and anotheridentical set was also fabricated. Both the sets were stuck to eachother with the 90° C. layers facing each other, to provide a symmetriccross-ply laminate of each substrate. The laminate was placed in a platemold, and a sealant and a bag material (polyamide film) were used forsealing to form a cavity. The cavity was provided with a suction portfor evacuation. A vacuum pump was used for evacuating the cavity fromthe suction port, to reduce the pressure to vacuum in the cavity, andthe preform mold was adjusted to 80° C. The laminate was kept in thisstate for 1 hour and cooled to room temperature, and the suction wasstopped. In this way, a quasi-isotropic preform A and a quasi-isotropicpreform B were obtained.

EXAMPLE 6

[0215] The carbon fiber reinforced substrate C and the carbon fiberreinforced substrate D were used. A stack architecture as stated inExample 5 was repeated three times to form a set. Another identical setwas also fabricated. Both the sets were stuck to each other to provide asymmetrical cross-ply laminate. A pressure of 150 kPa was applied to thelaminate at 130° C. using a press machine containing a preform mold for5 minutes, and in succession with the pressure kept as it was, thelaminate was cooled to room temperature and depressurized. In this way,a quasi-isotropic preform C and a quasi-isotropic preform D wereobtained.

EXAMPLE 7

[0216] A uni-directional preform A, a uni-directional preform B and auni-directional preform C were obtained as described for Example 5,except that four layers of a stack architecture of [0°] were used forthe carbon fiber reinforced substrate A and the carbon fiber reinforcedsubstrate B, and six layers of a stack architecture of [0°] were usedfor the carbon fiber reinforced substrate C.

EXAMPLE 8

[0217] Any of the quasi-isotropic preform A, the quasi-isotropic preformB, the quasi-isotropic preform C, the quasi-isotropic preform D, theuni-directional preform A, the uni-directional preform B and theuni-directional preform C was placed in a 80° C. mold, and a resindistribution medium (34-mesh wire net) was placed on the preform. Then,a sealant and a bag material (polyamide film) were used for sealing toform a cavity. The cavity was provided with a resin injection port and asuction port for evaluation. A vacuum pump was used for evacuating thecavity through the suction port, to reduce the pressure to vacuum in thecavity, and the mold and the preform were adjusted to 80° C. Then, thethird resin, preliminarily prepared and vacuum-degassed, was injectedfrom the resin injection port using the atmospheric pressure, whilebeing kept at 80° C. When the third resin reached the suction port forevacuation, the resin injection port was closed to stop the resininjection. Thereafter, while the cavity was continuously evacuated bythe vacuum pump from the suction port, the third resin impregnated intothe preform was cured with the temperature kept at 180° C. for 2 hours.In this way, a quasi-isotropic plate A, a quasi-isotropic plate B, aquasi-isotropic plate C, a quasi-isotropic plate D, a uni-directionalplate A, a uni-directional plate B and a uni-directional plate C wereobtained.

[0218] The volume fraction of carbon fibers Vf in the quasi-isotropicplate A was 54 vol %; the volume fraction of carbon fibers Vf in thequasi-isotropic plate B, 56 vol %; the volume fraction of carbon fibersVf in the quasi-isotropic plate C, 55 vol %; and the volume fraction ofcarbon fibers Vf in the quasi-isotropic plate D, 53 vol %.

[0219] The volume fraction of carbon fibers Vf in the uni-directionalplate A was 55 vol %; the volume fraction of carbon fibers Vf in theuni-directional plate B, 56 vol %; and the volume fraction of carbonfibers Vf in the uni-directional plate C, 56 vol %.

[0220] These composites were quite free from pinholes and voids, and itwas demonstrated that good molding was carried out.

[0221] From each of the obtained quasi-isotropic plate A,quasi-isotropic plate B, quasi-isotropic plate C and quasi-isotropicplate D, a 152 mm long×102 mm wide plate was cut out as a coupon. Aweight of 5.44 kg (12 lbs) was dropped to the center of the coupon, togive a drop weight impact of 6.67 kJ/m (1500 in·lb/in), and thecompression strength after impact (CAI) was measured.

[0222] Furthermore, from each of the obtained uni-directional plate A,uni-directional plate B and uni-directional plate C, a coupon inaccordance with SACMA SRM 1R-94 was obtained. The coupon was immersed in70° C. water for 14 days (hot-wet conditioning), and immediately the 0°compression strength of the coupon at evaluated temperature (82° C.)(CHW) was measured. Furthermore, the 0° compression strength of thecoupon of either the uni-directional plate A or the uni-directionalplate C at room temperature (CS), not subjected to hot-wet conditioning,was also measured.

[0223] Moreover, from each of the uni-directional plate A, theuni-directional plate B and the uni-directional plate C, a coupon inaccordance with SACMA SRM 4R-94 was obtained. The 0° tensile strength ofthe coupon at room temperature (TS) was measured.

COMPARATIVE EXAMPLE 1

[0224] The uni-directional woven fabric A produced as described forExample 1, except that the first resin A was not caused to adhere, wasused as a carbon fiber reinforced substrate E.

COMPARATIVE EXAMPLE 2

[0225] The carbon fiber bundles C were used as warp yarns and the glassfiber bundles were used as auxiliary weft yarns, to form auni-directional woven fabric F. The woven fabric F was a plain weave,and had a thickness of 0.2 mm, a carbon fiber unit weight of 193 g/m²,4.87 warp ends/cm and 3 weft ends/cm. A carbon fiber reinforcedsubstrate F was obtained as described for Example 1, except that 100parts by weight of the woven fabric F were coated with 5 parts by weightof the first resin C.

COMPARATIVE EXAMPLE 3

[0226] A quasi-isotropic preform E, a quasi-isotropic preform F, auni-directional preform E and a uni-directional preform F wererespectively obtained, as described for processing the carbon fiberreinforced substrate A and the carbon fiber reinforced substrate C,except that the carbon fiber reinforced substrate E and the carbon fiberreinforced substrate F were used.

COMPARATIVE EXAMPLE 4

[0227] A quasi-isotropic plate E, a quasi-isotropic plate F, auni-directional plate E and a uni-directional plate F were respectivelymolded as described for Example 8, for testing, except that thequasi-isotropic preform E, the quasi-isotropic preform F, theuni-directional preform E and the uni-directional preform F were used.The volume fraction of carbon fibers Vf in the quasi-isotropic plate Ewas 59 Vol %, and the volume fraction of carbon fibers Vf in thequasi-isotropic plate F, 56 vol %. The volume fraction of carbon fibersVf in the uni-directional plate E was 60 vol %, and the volume fractionof carbon fibers Vf in the uni-directional plate F, 56 vol %.

[0228] The results of the above are shown in Table 1. TABLE 1 Propertiesof carbon fiber bundles Deposited Deposited Tensile modulus (GPa) amountof first amount of second Fracture strain resin (parts by resin (partsby Substrate energy (MJ/m³) weight) weight) A 294 10 Nil 58 B 294 7 7 58C 294 14 Nil 58 D 235 5 Nil 53 E 294 Nil Nil 58 F 235 5 Nil 27 Handlingproperties CAI CHW CS TS of (Mpa) (Mpa) (Mpa) (Mpa) Substrate substrate(ksi) (ksi) (ksi) (ksi) A Good 248 972 1428 2766 36 141 207 401 B Good276 1028 — 2808 40 149 — 407 C Good 282 952 1421 2966 41 138 206 430 DGood 232 — — — 34 — — — E No good 165 1041 — 2738 24 151 — 397 F Good109 996 — — 16 144 — —

[0229] As can be seen from Table 1, the carbon fiber reinforcedsubstrates A, B, C and D were easier to handle than the substratesproduced using prepregs, owing to the first resin adhering to each wovenfabric. They were very excellent in such handling properties asstiffness, form stability of woven fabric in terms of texture slippageand misalignment, portability and drapability. When they were formedinto preforms, they exhibited excellent tackiness, and the carbon fiberreinforced substrate laminates obtained from them were not delaminated.Thus, strong bulky preforms could be obtained.

[0230] On the other hand, the carbon fiber reinforced substrate E devoidof the first resin was poor in handling properties, and since it was nottacky, the respective layers were delaminated, not allowing a bulkypreform to be obtained.

[0231] In view of mechanical properties, the carbon fiber reinforcedsubstrates A, B, C and D in conformity with the invention wereremarkably higher in CAI, and yet not lower in CHW or TS than the carbonfiber reinforced substrate E. On the other hand, the carbon fiberreinforced substrate F not in conformity with the invention was verypoor especially in CAI, being unsuitable for applications such asstructure elements requiring high mechanical properties, even though itcontained the first resin.

[0232] Industrial Applicability

[0233] The invention can provide a composite good in matrix resinpermeability and excellent in mechanical properties such as thecompression strength after impact and the compression strength afterhot-wet conditioning at high productivity. In addition, the inventioncan provide a carbon fiber reinforced substrate excellent in stiffness,form stability, drapability and tackiness in lamination, a preformformed by laminating layers of the substrate, and a composite obtainedby impregnating the preform with a matrix resin.

[0234] The composite obtained like this is suitable as any of variouselements such as a structure element, interior element and exteriorelement in such transport machines as aircrafts, motor vehicles andships and other wide areas. It is especially suitable as a structureelement of an aircraft.

1. A carbon fiber reinforced substrate comprises a fabric composed ofcarbon fiber bundles and a first resin adhering to said fabric, whereinsaid carbon fiber bundles respectively comprises numerous continuouscarbon filaments, the tensile modulus of said carbon fiber bundles is210 GPa or more, the fracture strain energy of said carbon fiber bundlesis 40 MJ/m³ or more, and the amount of said first resin adhering to saidfabric is in a range from 1 to 20 parts by weight per 100 parts byweight of said fabric.
 2. A carbon fiber reinforced substrate accordingto claim 1, wherein the amount of said first resin is in a range from 1to 10 parts by weight per 100 parts by weight of said fabric.
 3. Acarbon fiber reinforced substrate according to claim 1, wherein thefirst resin adhering to said fabric adheres relatively more densely on asurface of said fabric than in the inside of said carbon fiber bundles.4. A carbon fiber reinforced substrate according to claim 1, whereinsaid tensile modulus of said carbon fiber bundles is in a range frommore than 280 to less than 500 GPa, and the fracture strain energy ofsaid carbon fiber bundles is 53 MJ/m³ or more.
 5. A carbon fiberreinforced substrate according to claim 1, wherein said fabric is auni-directional woven fabric, bi-directional woven fabric oruni-directional sheet, the carbon fiber unit weight of the carbon fibersubstrate is in a range from 50 to 500 g/m², and the thickness of thecarbon fiber substrate is in a range from 0.1 to 0.8 mm.
 6. A carbonfiber reinforced substrate according to claim 1, wherein said fabric isa uni-directional woven fabric or uni-directional sheet, and the airpermeability of the carbon fiber substrate is in a range from 10 to 200cm³/cm²·sec.
 7. A carbon fiber reinforced substrate according to claim1, wherein said first resin is studded on a surface of said fabric, andthe diameters of the studded pieces are 1 mm or less.
 8. A carbon fiberreinforced substrate according to claim 1, wherein said first resindiscontinuously adheres on a surface of said fabric.
 9. A carbon fiberreinforced substrate according to claim 1, wherein said first resinadheres on a surface of said fabric, and the average thickness of thefirst resin adhering on the surface is in a range from 5 to 250 μm. 10.A carbon fiber reinforced substrate according to claim 1, wherein themelting point or flow initiation temperature of said first resin is in arange from 50 to 150° C.
 11. A carbon fiber reinforced substrateaccording to claim 1, wherein the main component of said first resin isa thermosetting resin.
 12. A carbon fiber reinforced substrate accordingto claim 1, wherein the main component of said first resin is athermoplastic resin.
 13. A carbon fiber reinforced substrate accordingto claim 12, wherein the amount of said thermoplastic resin is in arange from 70 to 100 wt % based on the weight of said first resin.
 14. Acarbon fiber reinforced substrate according to claim 1, wherein the maincomponent of said first resin is at least one selected from the groupconsisting of epoxy resins, polyamide resins, polyetherimide resins,polyphenylene ether resins, polyether sulfone resins and phenoxy resins.15. A carbon fiber reinforced substrate according to claim 1, whereinthe amount of a second resin higher in melting point or flow initiationtemperature than said first resin and adhering to said fabric is in arange from 1 to 10 parts by weight per 100 parts by weight of saidfabric.
 16. A carbon fiber reinforced substrate according to claim 1,wherein the amount of a second resin neither molten nor caused to flowat the melting point or flow initiation temperature of said first resinand adhering to said fabric is in a range from 1 to 10 parts by weightper 100 parts by weight of said fabric.
 17. A carbon fiber reinforcedsubstrate according to claim 15 or 16, wherein said second resin adhereson a surface of said fabric by means of said first resin.
 18. A carbonfiber reinforced substrate according to any one of claims 15 through 17,wherein said second resin is particles with an average particle diameterof 1 to 500 μm.
 19. A carbon fiber reinforced substrate according to anyone of claims 15 through 18, wherein the main component of said secondresin is a thermoplastic resin.
 20. A carbon fiber reinforced substrateaccording to any one of claims 15 through 19, wherein the main componentof said second resin is at least one thermoplastic resin having a glasstransition temperature of 30 to 280° C. selected from the groupconsisting of polyamide resins, polyamideimide resins, polyetherimideresins and polyether sulfone resins.
 21. A perform comprises a laminatecomprising at least two or more layers of the carbon fiber reinforcedsubstrate as set forth in any one of claims 1 through 20, wherein thelayers of the carbon fiber reinforced substrate are integrally bonded toeach other by means of said first resin or second resin.
 22. A compositecomprises at least the preform as set forth in claim 21 and a thirdresin, wherein said preform is impregnated with a third resin differentfrom said first resin.
 23. A composite according to claim 22, which isused as any one of a primary structure element, secondary structureelement, exterior element, interior element and parts forming thoseelements in an aircraft, a motor vehicle or a ship.